Use a special program for smartphones that allows you to remotely control all kinds of sounds and notify you about them. SkypeSpy can be used as alarm system for home or office, can monitor the child's condition, and, of course, it can be used as a wire.
Locate your smartphone with the software installed in the place where you have to control the sounds (in the children's room, office, car, etc.). Communications program connects to another device and when it detects any sound, the smartphone sends an SMS, MMS or calling. Such programs can be found on ExSmart.Net, smart60.ru, alldown.ru , M-TEL.ru, dimonvideo.ru.
If it is necessary to carry out the wiretapping of the home phone modem, download the program ModemSpy. Install it on your computer. Select File -> Preferences, in the Hardware tab, select your modem. In the Recording tab to configure recording modes of conversation.
Using the first setup, you can put on the machine all incoming and a timer recording has started. The second is responsible for outgoing calls. The last setting is responsible for the filter capture files of a certain size. Less software is impossible to record and listen to the conversation at the same time, as they can get stuck in it and discover yourself. Download link of the program - http://www.izone.ru/business/communication/modem-spy.htm.
If you want to make a wire with their hands, use schemes of manufacturing of bugs for wiretapping. A lot of them online, from elementary to professional. This will require certain skills and experience in electronics.
If you want to install the wire in the next room, use the microphone and recording device (up to player). You can install such a device on the Cabinet or in the ceiling or wall and bring the wires into the next room, where you want to go signal.
Use the paddles - - stat. Primitive method on the principle of "glass door", but, oddly enough, works. But that's just in emergency situations, but do not have to spend money on expensive equipment or computer programs.